Metal-to-metal sealing is commonly used in subsea hydrocarbon production assemblies. For example, subsea wells typically have a subsea wellhead assembly at the seafloor with a subsea production tree mounted on the wellhead assembly. The tree has valves connected to flowlines for controlling flow from the well. In another type of installation, a string of tieback conduit extends from the subsea wellhead assembly to a platform at the surface. A surface tree is mounted on the upper end of the tieback conduit. Some riser systems have inner and outer tieback conduits, each of which is run separately and connected by a tieback connector. The inner and outer tieback conduits make up the tieback riser in that type of system.
The inner tieback conduit is installed by connecting a tieback connector to the lower end of the conduit and lowering it into the bore of the subsea wellhead housing assembly. The tieback connector has a locking member that locks to the subsea wellhead housing or to the tapered stress joint at the bottom of the outer tieback conduit. The inner tieback connector also includes a seal between where the tieback connector lands onto the subsea wellhead assembly. The seal is preferably a metal-to-metal seal, and it seals to an internal component of the subsea wellhead housing assembly. Metal-to-metal seals have a variety of configurations. While many work well, improvements are desired.